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Started by PDR, April 13, 2020, 18:23:59 pm

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PDR

What with the perfect flying weather over the weekend being wasted because I can't leave the grounds, I was suffering SFWS (serious flying withdrawal syndrome). Yesterday I did some messing around in the garden with a 200g quad, which is OK for a quick fix but the controls are too dumbed-down to be interesting for long. So I today finished off the refurbishment/upgrade of one of my ancient Kyosho EP Concept Helis (a project that's been running on and off for about 10 years).

It still has the original Futaba FPS-143 servos, but I've bunged in a brushless motor (a Turnigy 3,000rpm/v outrunner) and fettled a battery mount (and canopy) to take a 3s3000 lipo rather than the original 8 cell 1700mAh nicad. I've also replaced the original mechanical gyro with an Telebee RCS500 dual-mode solid-state one. And of course it has a top-of-the-range 2.4g receiver (Orange 9ch DSMX). The rest of the job was just making mounting systems to move the bits around to get a good CG, and a general check/clean/lube.  The gyro is one I bought maybe 15 years ago to use in a stabilised video camera mount it worked, but I found a better way of doing it so I put it back in the box and forgot about it.

I spent a couple of hours carefully setting up centring, levelling the swashplate, checking travels etc. I set the gyro ATV to just a smidge less than mechanical maximum, and confirmed all the directions were correct. I set the aileron and elevator throws at max available travel, because I don't remember these things ever being what you might call "twitchy"(!). As originally fitted and flown the pitch range went from -2 to +11 degrees. That should certainly fly, but I have a feeling I might want a bit more negative to stop the rotor RPM decaying in descents (this isn't really an aerobatic heli).

So having done all that I popped onto the drive just to give it a quick spin-up to check for balance and get a starting point for the gyro gain. The blades I fitted were a rather tatty set of the original plastic ones, but they balanced OK. The battery was one from the box - charged to storage level about 4 months ago, and used for all the radio set-up process. On my MPX Evo transmitter I set up one slider for gyro gain (down for rate, up for HH) just for initial setting up. Once I have a value for this I'll put that on a fixed flight-phase setting and re-allocate that slider to collective trim. The other slider I've used for the throttle-limiter. I set the gyro to about 50%HH and the throttle limiter to 40% to ensure it wouldn't lift off.

As it spun up there was the usual shuddering, but once the rotors were going a bit faster it all smoothed out. I brought the collective up to about 50% to make it a bit lighter on the skids to see if any tail-wag might become evident on the smooth tarmac. At least that was the plan. What actually happened was it lifted off and sat nicely at about 18" off the deck, reasonably solid in the slightly blustery breeze, very controllable and with just a hint of tail wag. I was just thinking that this was flying really nicely and preparing to lift it higher to fly away when I remembered that the throttle limiter was at 40%, and the battery was at half charge. So I set it down and switched off!

It looks like this will be usable for some back-garden flying, but I'll need to cautiously increase the throttle limit setting (not sure what sort of RPM these blades can take) and consider a smaller pinion. But for a 30-year-old relic I think it did quite well...

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

PDR

April 18, 2020, 19:29:51 pm #1 Last Edit: April 18, 2020, 19:30:54 pm by PDR
Well I got the Concept in the garden with a fresh battery and a pair of "New" (unused in original packaging, but probably 25 years old) blades:



I set the throttle limiter to about 60%, gyro gain at 50% and brought the collective to neutral. It all spun up, running smoothly so with some more collective it gently settled at around 6 foot up. Stable, flying happily and responding nicely to the controls with just a dab of tail trim. I was just thinking about moving off up the garden when BANG!! Something flew over my head and the model did its finest brick impression:



The damage isn't actually too bad - a tail boom, the blades, one cracked blade holder and the complete annihilation of the tailplane. But the worrying thing was the cause of the crash. The think that whizzed over my head was one of the main blades. It just let go and set off for Frensham, doing reasonably well until a tree reminded it that under the lock-down rules it wasn't allowed to leave the property. These blades have a foam core with a 2.5mm steel wire leading edge and moulded nylon root, with plastic shells bonded over the top in a press (I think). I had always assumed the inner end of the steel leading edge was bent into a U=shape that wrapped around the attachment bolt, but it seems that I was wrong. It's actually got a rolled thread that is self-tapped into the nylon root fitting. What seems to have happened is the root fitting has split - the material doesn't seem very strong, and I wonder if it's degraded due to age. Whatever the reason, the blade just pulled out and ran away:



A very lucky escape, although my practice of not doing sustained hovering below 6' in case it throws anything seems to have been justified here!

I do have the spares to rebuild, but I no longer trust the stock blades so I will need to find something else to use instead before I try...

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

lanicopter

Good call on flying above head height. These things always make me nervous for precisely that reason - I've watched quite a few Youtube videos of scale helicopters where spectators aren't that far away from the aircraft and it's enough to make you cringe inside.

Current fuel status: "Master Caution"

paulinfrance

It's a good job you were confined, it saved other club members,, :'' 

So next job glue some samba and balsa together and make your own ?. :study:

I had this happen to a friends new Raptor .90, we ( me ) ran the engine up without the new fb blades to run and regulate the motor, after a tank full of fuel I bolted the blades on and put the helicopter in the middle of the runway and walked back behind the steel safety grill, I ran the engine up 1/2 throttle and "Bang", one blade hit the fence in front of us and the helicopter went into self destruct mode, Frightening with a .90 size helicopter,, :-\
Mode 2 THE only way to fly

lanicopter

Could have been worse

Current fuel status: "Master Caution"